a. Field of the Invention
This disclosure relates to a medical device stabilization system and methods for use (e.g., for minimally invasive heart surgery) for a wide variety of devices such as an ablation catheter which may be temporarily anchored to or biased toward an organ or the targeted tissue of the organ for medical procedures.
b. Background Art
Normal heart rhythm is between 60 and 100 beats per minute. Tachycardia is a fast heart rate (usually over 100 beats per minute) caused by disease or injury. Tachycardias may begin in the upper chambers of the heart (the atria) or the lower chambers of the heart (the ventricles). Some tachycardias are harmless, but other tachycardias are life threatening. With this disorder, the heart does not fill with enough blood between beats to meet the needs of the body. Tachycardias can quickly deteriorate to fibrillation.
Atrial fibrillation (AF) is the most common abnormal heart rhythm. It is a very fast, uncontrolled heart rhythm that occurs when the upper chambers of the heart (the atria) try to beat so fast (between 350 and 600 times per minute) that they only quiver and fail to effectively pump blood to the organs and other tissues of a subject. Ventricular fibrillation (VF) occurs when the lower chambers of the heart (the ventricles) produce impulses that make the heart beat too quickly. Fibrillation is a life-threatening arrhythmia demanding immediate treatment.
Before a tachycardia deteriorates to fibrillation, various procedures may be used to treat the heart tissue and reduce or altogether eliminate the occurrence of fibrillations. It is well known that treatment benefits may be gained by forming lesions in tissue if the depth and location of the lesions being formed can be controlled. These lesions block the errant electrical signals that result in the tachycardia. In particular, it can be desirable to elevate tissue temperature until thermally necrosed lesions are formed which change, i.e. reduce or eliminate the electrical conductivity of the tissue. For example, when “adequate” or “sufficiently deep” lesions are formed at specific locations in cardiac tissue, undesirable fibrillations may be permanently reduced or eliminated. The definition of “adequate” or “sufficiently deep” when describing lesion formation depends at least to some extent on the procedure and may also depend on other considerations, such as tissue characteristics and desired results. In general it is currently thought that transmural lesions are desired (i.e., lesions extending between the endocardium and the epicardium). However some recently reported work demonstrates this may not always be true.
Several difficulties may be encountered with existing ablation or lesion-making techniques. For example, during minimally invasive surgical (MIS) ablation procedures on a patient's heart, a physician makes a small incision in the patient's abdomen for insertion of an ablation device. The ablation device may have a high intensity focused ultrasound (HIFU) electrode on the tip for delivering ablative energy to the heart tissue. The physician must maneuver the tip of the ablation device adjacent the heart tissue to be ablated (the “target tissue”). The physician may determine placement of the ablation device based on his/her experience maneuvering the ablation device during the ablation procedure. Such experience only comes with time, and may be quickly lost if the physician does not perform ablation procedures on a regular basis. In the case of MIS procedures the target tissue is not in the surgeon's direct line of sight.
Even an experienced physician may find it difficult to maneuver the ablation device. For example, an extended ablation device inserted through a small incision in the patient's abdomen severely limits the physician's ability to manipulate the tip of the ablation device in the desired direction near or on the heart. In addition, the axis of the ablation device may not be aligned with the desired lesion axis, thereby requiring the physician to reposition the ablation device so that the physician can pull the ablation device in the direction needed to form a linear or curvilinear lesion. Even after properly positioning the ablation device, it is often difficult to drag the ablation device at a constant velocity and at the appropriate angle to achieve a uniformly deep and wide lesion.
When these procedures are performed on the heart, the beating heart further complicates matters by making it difficult to assess placement of the ablation device adjacent the tissue during the time needed to form the desired lesion. That is to say that one would not want the ablation device moving uncontrollably, as by random lateral slippage or sliding, during the procedure. If the ablation device is not properly controlled, a quality lesion is unlikely to be formed and the procedure may be unsuccessful, needing to be repeated to achieve the desired result. In addition, there may be undesirable damage to the surrounding tissue.
Thus, there remains a need for controlled placement of a stationary or otherwise fixed ablator (relative to the tissue to be ablated) for ablation procedures.